Second Battle of Arras

The Second Battle of Arras was fought from 9 April to 16 May 1917 on the Western Front of World War I. The British Army launched a diversionary attack on German positions concurrent with the French Army's Nivelle Offensive, and, while the British achieved limited progress, they failed to make a decisive breakthrough, and they suffered heavy losses in the process.

Background
The Battle of Arras was undertaken by the British to support a French offensive on the Aisne River. In early 1917, French commander-in-chief Robert Nivelle claimed he could achieve a breakthrough at the Aisne River. British commander Field Marshal Douglas Haig agreed to support Nivelle by making diversionary attacks at Arras and Vimy Ridge. Canadian troops were chosen to lead the assault on Vimy Ridge. They had already participated in the Battle of Neuve Chapelle, the Second Battle of Ypres, and the Somme.

Meanwhile, in March 1917, the Germans withdrew to the Hindenburg Line, a series of fortifications they built in northeastern France, and abandoned the area between Arras and the Aisne.

Battle
The British Army had learned many lessons in the nine months since the disastrous first day of the Somme. The attack at Arras was still preceded by a five-day artillery bombardment, which sacrificed the element of surprise, but it was far more effective than at the Somme. The British gunners could identify the exact positions of German batteries by using sound-ranging techniques, which analyzed the sounds of the guns, and "flash-spotting" - observing the flashes when enemy guns were discharged.

The British also had shells with new "graze" fuses that exploded on touching barbed wire, enabling the artillery bombardment to clear the wire in front of enemy trenches more effectively. Meanwhile, engineers excavated tunnels leading to the British front line, linking up existing caves nad quarries into an underground system so that thousands of soldiers could assemble in forward positions unobserved by the enemy on high ground. Saps (short trenches) were dug into no man's land to provide jumping-off points from which to rush the enemy trenches.

Dawn attack
The offensive was launched at dawn on 9 April, a bitterly cold Easter Monday, amid sleet and flurries of snow. Through good coordination with the artillery, the infantry were able to advance as close as 50 yards behind the creeping barrage laid down by the gunners, who mixed gas shells with high explosives for maximum effect. Four divisions of the Canadian Corps were tasked with seizing Vimy Ridge, an obstacle that had resisted all previous attacks. Wellt rained and led, the Canadians had taken the crest of the ridge by late afternoon and were looking down on retreating Germans on the plain beyond. There were further advances by the British 3rd Army on the Canadians' right.

Once through the German front line, British infantry advanced in places to a depth of over 3 miles, using flexible small-unit tactics to surround and overcome fortified strongpoints and machine gun nests. About 9,000 German prisoners were taken on the first day and many guns were captured. The Germans were partly undone by their own tactics. The German army had adopted the principle of "defense in depth." This meant that frontline positions were to be relatively lightly held, with counterattack forces rushing forward from the rear to retake ground once the enemy attack lost momentum. But at Arras the counterattacking rserves were held too far back, leaving outnumbered, unsupported German frontline troops to suffer grievous losses.

False hope
The appearance of a major British victory soon proved ill-founded. General Edmund Allenby, commanding the Third Army, was slow to seize the opportunity to press on with the advance, then overoptimistic when it was too late. On 11 April, he told hi men they were pursuing a defeated enemy and brought forward the cavalry to exploit the breakthrough. By that time, however, German reserves were arriving and progress stalled. At the southern end of the line, Australian troops sent to attack at Bullecourt on 10-11 April were caught up in a confused slaughter that recalled the Somme. Artillery was inadequate, barbed wire was uncut, and tanks arrived too late to forge a path for the ANZAC infantry. The attack failed and the Australians suffered their heaviest single-day losses of the war.

Meanwhile, a savage air battle raged overhead. The British Royal Flying Corps, commanded by General Hugo Trenchard, was relentlessly active in support of the army, carrying out photoreconnaissance, acting as aerial observers for the artillery, and attacking ground targets. German antiaircraft fire and fighter aircraft, including Baron Manfred von Richthofen's squadron, took a heavy toll on the inferior British aircraft. Heavy losses of aircrew led to novice British pilots being thrown into combat with little chance of survival.

Lost cause
British commander-in-chief Field Marshal Douglas Haig insisted on continuing the Arras operation into May as a gesture of support for the French, who were heavily engaged in the Nivelle Offensive to the south. British casualties mounted sharply for insignificant gains. By the time the operation was halted on 16 May, the British Army had suffered more than 150,000 casualties, including 11,000 Canadians. German losses probably numbered around 130,000.

Aftermath
The Battle of Arras and the French Nivelle Offensive marked a shift in the balance between British and French forces on the Western Front. The British Army had acted as a junior partner in the alliance with the French since 1914. However, after the failure of the Nivelle Offensive and the subsequent mutinies in the French Army, Britain took lead responsibility for offensive operations. After a success at Messines in June 1917, Haig launched a large-scale offensive at the Ypres salient at the end of July. Continuing until November, the notorious bloodbath that followed became known as the Battle of Passchendaele. The Germans reflected hard upon their initial setbacks at Arras and Vimy Ridge, refining their strategy of defense in depth to improve its effectiveness.